Project Summary/Abstract The overarching goal of this project is to take the preliminary steps to develop new non-human primate (NHP) models of outer retinal degeneration compatible with safety and efficacy assessment of stem cell-derived photoreceptor transplantation. Inherited retinal degenerations such as rod-cone dystrophy are a major cause of human blindness caused by a large number of mutations in over 200 genes expressed in the retina ? some of which have not yet been identified. These diseases do not spontaneously occur in non-human primates, making it difficult to evaluate cell replacement as a potential therapeutic avenue in a relevant large animal model with a macula. We propose to generate macaque models with outer retinal degeneration and evaluate them for their utility to study the short- term feasibility of photoreceptor transplantation. Implanting a silicon sheet underneath the retina of normal macaques will generate a first mechanical injury model by impeding contact between photoreceptors (PRs) and retinal pigment epithelium (RPE). Our prior studies involving subretinal implants demonstrated the high short-term feasibility of this approach in generating local photoreceptor degeneration as early as one-month post surgery. In parallel, we will assess outer nuclear degeneration via a genetically encoded photosensitizer expressed exclusively in photoreceptors after AAV mediated delivery. This second model will display outer retinal cell loss in response to illumination. Retinal thinning will be visualized in vivo using optical coherence tomography. Once outer retinal cell loss has been obtained in macaques using these strategies, we will transplant human induced pluripotent stem cell- derived photoreceptors underneath the degenerated zone. This will answer the questions: 1- can the retina can tolerate two subretinal procedures? 2- which model is best suited for assessing? The two models we aim to create will display large zones of outer retinal degeneration compatible with behavioral testing after photoreceptor transplantation. In our follow up project, we will evaluate the survival and structure of the transplanted cells with in vivo imaging, while the functionality will be assessed with physiological tests. Animals and methods for generating the macaque models will be made available to research investigators either for independent or collaborative studies aimed at understanding the molecular mechanisms involved in photoreceptor cell loss, and for developing restorative therapies that can be evaluated on a short- or long-term basis. Our proposal will provide support for the principal hypothesis that collaborative research using these non-human primate models, with an experienced team of investigators, will lead to critical proof-of-principle studies directed at developing safe and effective regenerative therapies for human retinal degenerations. ! !